Properly handle null FactoryBean instance

Issue: SPR-16250

Author: jhoeller

spring-beans/src/main/java/org/springframework/beans/factory/support/AbstractBeanFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -552,7 +552,7 @@ else if (containsSingleton(beanName) && !containsBeanDefinition(beanName)) {
 
 		// Check bean class whether we're dealing with a FactoryBean.
 		if (FactoryBean.class.isAssignableFrom(beanType)) {
-			if (!BeanFactoryUtils.isFactoryDereference(name)) {
+			if (!BeanFactoryUtils.isFactoryDereference(name) && beanInstance == null) {
 				// If it's a FactoryBean, we want to look at what it creates, not the factory class.
 				beanType = getTypeForFactoryBean(beanName, mbd);
 				if (beanType == null) {
@@ -1614,8 +1614,13 @@ protected Object getObjectForBeanInstance(
 			Object beanInstance, String name, String beanName, @Nullable RootBeanDefinition mbd) {
 
 		// Don't let calling code try to dereference the factory if the bean isn't a factory.
-		if (BeanFactoryUtils.isFactoryDereference(name) && !(beanInstance instanceof FactoryBean)) {
-			throw new BeanIsNotAFactoryException(transformedBeanName(name), beanInstance.getClass());
+		if (BeanFactoryUtils.isFactoryDereference(name)) {
+			if (beanInstance instanceof NullBean) {
+				return beanInstance;
+			}
+			if (!(beanInstance instanceof FactoryBean)) {
+				throw new BeanIsNotAFactoryException(transformedBeanName(name), beanInstance.getClass());
+			}
 		}
 
 		// Now we have the bean instance, which may be a normal bean or a FactoryBean.

spring-beans/src/main/java/org/springframework/beans/factory/support/DefaultListableBeanFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -739,19 +739,22 @@ public void preInstantiateSingletons() throws BeansException {
 			RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
 			if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
 				if (isFactoryBean(beanName)) {
-					final FactoryBean<?> factory = (FactoryBean<?>) getBean(FACTORY_BEAN_PREFIX + beanName);
-					boolean isEagerInit;
-					if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
-						isEagerInit = AccessController.doPrivileged((PrivilegedAction<Boolean>) () ->
-								((SmartFactoryBean<?>) factory).isEagerInit(),
-								getAccessControlContext());
-					}
-					else {
-						isEagerInit = (factory instanceof SmartFactoryBean &&
-								((SmartFactoryBean<?>) factory).isEagerInit());
-					}
-					if (isEagerInit) {
-						getBean(beanName);
+					Object bean = getBean(FACTORY_BEAN_PREFIX + beanName);
+					if (bean instanceof FactoryBean) {
+						final FactoryBean<?> factory = (FactoryBean<?>) bean;
+						boolean isEagerInit;
+						if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
+							isEagerInit = AccessController.doPrivileged((PrivilegedAction<Boolean>) () ->
+											((SmartFactoryBean<?>) factory).isEagerInit(),
+									getAccessControlContext());
+						}
+						else {
+							isEagerInit = (factory instanceof SmartFactoryBean &&
+									((SmartFactoryBean<?>) factory).isEagerInit());
+						}
+						if (isEagerInit) {
+							getBean(beanName);
+						}
 					}
 				}
 				else {

spring-context/src/test/java/org/springframework/context/annotation/ConfigurationClassPostProcessorTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -1132,6 +1132,11 @@ public static class RepositoryFactoryBeanConfiguration {
 		public RepositoryFactoryBean<Object> repoFactoryBean() {
 			return new RepositoryFactoryBean<>();
 		}
+
+		@Bean
+		public FactoryBean<Object> nullFactoryBean() {
+			return null;
+		}
 	}
 
 	@Configuration